Lithium ions have been found to be effective agents for the treatment of bipolar manic-depression. Lithium is also fairly effective as prophylactic for some forms of monopolar depression and is used nowadays in the treatment of a very large number of patients all over the world. The mode of action of lithium is not adequately understood.
The major shortcomings of the "lithium therapy" are the large dosages required (of the order of some grams per day) and the delayed onset of the effect. Both disadvantages are due to the slow penetration of lithium through the blood brain barrier and through other hydrophobic layers and membranes of the central nervous system. The high dosages necessary causes lithium build-up in organs such as the liver, kidneys and in the thyroid, resulting in effects such as thirst, gain of weight and thyroidal disorders.